U.S. Pat. No. 3,320,124 (American Cyanamid Co.) disclosed the activity against coccidiosis exerted by compounds of formula: ##STR2## wherein: R'=H, halogen, nitro, benzo, alkyl, phenyl and alkoxy;
R"=hydroxy, acetoxy and alkoxy; PA1 R"'=H, alkenoxycarbonyl. PA1 n is zero, one or two; PA1 R.sup.1 is a hydrogen atom or an alkyl C.sub.1 -C.sub.4 ; PA1 R.sup.2 is a hydrogen atom, an alkyl C.sub.1 -C.sub.8, a cycloalkyl C.sub.3 -C.sub.6 or a phenyl optionally substituted by one or more alkyl C.sub.1 -C.sub.4 or halogen atoms;
The compounds of formula II in which R"'=H, already known as antimalarial compounds (U.S. Pat. No. 2,694,711 American Cyanamid Co.), were obtained by optimization of the antimalarial activity of febrifugine (II, R'=H, R"=OH, R"'=H), a natural alkaloid contained in the inflorescence of Dichroa febrifuga, originally of China and used as antimalarial agent in the pharmacopoeia of said country.
Among the compounds of formula II, the compound commonly known as "Halofuginone" (II, R'=6-Cl, 7-Br; R"=OH; R"'=H) developed by Roussel-Uclaf, proves to be particularly active against coccidiosis in poultry.
Halofuginone possesses a high anticoccidial activity even at very low doses (the practical dose of 3 ppm in the feed is suggested), but it is affected by the drawback of being very toxic for chickens (LD.sub.50 =17.6 mg/Kg). Its low dose of use causes some practical difficulties as, if the admixing to the feed is not perfectly accomplished, the assumption of the product by the chicken may be insufficient, wherefore the animal is not protected from coccidiosis.
On the other hand it is not possible to obviate the risk of under-dosage by excessively increasing the dose of the product because of the toxicity of this toward poultry.
In British Patent Application No. 2,057,439 (Hoechst Co.) there are described some derivatives of the compounds of U.S. Pat. No. 2,694,711 and salts thereof, amongst which also the oxime derivatives. Said compounds are useful in the treatment of theileriasis, a desease of cattle, goats, and sheep which is transmitted by ticks. No anticoccidial activity is disclosed for them.